The Fontan procedure is currently standard care for patients with complex single ventricle congenital heart defects. The Fontan procedure involves the creation of a cavopulmonary (CP) shunt connecting the inferior and superior vena cava (IVC and SVC) directly to the right pulmonary artery (RPA), diverting total venous return from the IVC/SVC directly to the PA without entering the right atrium (RA) and right ventricle (RV). The Fontan procedure results in a blood flow pattern of a passively filled pulmonary circulation and a single ventricle to pump blood to the systemic circulation. Although it has improved thousands of patients'quality of life by increasing arterial O2 saturation, the mortality is reported at 29.1%1. Patients with a failing Fontan follow a bimodal distribution with some failing acutely in the early post-operative period and others are failing years later2, 3. Cavopulmonary assistance (CPA) is highly desired to effectively pump venous blood through the Fontan connection to the pulmonary artery and to reverse the pathophysiology of the failing Fontan circulation. However, there is currently no specific device available for CPA. Our objective in this Phase I STTR is to develop and fabricate a working prototype of a percutaneous double lumen cannula (DLC) for CPA and to test this prototype in our new failing Fontan sheep model. Our ultimate goal is to develop a CPA system that avoids the need for an open surgical procedure or the use of cardiopulmonary bypass (CPB). The enabling technology will be a percutaneous DLC that will drain venous blood from both the IVC and SVC simultaneously and infuse blood directly into the pulmonary artery. Our Specific Aims are: 1) to develop and fabricate a working prototype of a percutaneous DLC to assist failing Fontan circulation, and 2) to test our prototype CPA DLC in our improved failing Fontan sheep model. Our proposed cannula-based CPA will be a "game changer" in the management of failing Fontan physiology. PUBLIC HEALTH RELEVANCE: We are proposing to develop a percutaneous Cavopulmonary assistance system to bridge the patients with failing Fontan circulation for recovery, reconstructive surgery and heart transplantation.